Postgres Indexing: When Does BRIN Win?(crunchydata.com)

27 pointsby krnaveen14vor 4 Jahren6 comments

https://www.crunchydata.com/blog/postgres-indexing-when-does-brin-win

6 comments

aspyctvor 4 Jahren

Oh nice, I have just the tables for that! Billions of well-compacted rows with a big ol' timestamp on them. Btree indices are almost as big as the table itself...

Strum355vor 4 Jahren

Note that if you delete entries in non sequential order (aka not at the start-only or the end-only) and continue inserting, BRIN index becomes much less effective. Its very much predicated upon the concept of append-only, as postgres filling deleted rows with new rows throws off the physical layout part of how BRIN works

aspyctvor 4 Jahren

I don't delete anything in those tables, however I do one update on 9/10 of the rows, at least.

I seem to remember there was a way to reorder rows in a table, maybe that could be useful.

pramseyvor 4 Jahren

You can check if your data remain correlated after your updates. It's possible they do: SELECT correlation FROM pg_stats WHERE tablename = 'mytable' AND attname = 'mytimestamp';

aspyctvor 4 Jahren

Oh nice! I had no idea, I'll try it, thanks :)

geordeevor 4 Jahren

This is similar to Zone Maps in Netezza. https://www.ibm.com/docs/en/psfa/7.2.1?topic=statistics-zone...

Incidentally, Netezza was built on Postgres engine, years back.